Catalytic dewaxing of lubes in reactor fractionator

DETAILED DESCRIPTION It has now been demonstrated that a hydrotreater/hydrocracker combination can be so operated that it functions as distillation column as well as a reactor to discharge separate distillate and residual fractions.
The system of this invention provides a temperature gradient similar to that of a distillation column, maximum temperature in the bottom, thus affording maximum severity of treatment for the heavy fraction of the charge.
Application of the new technique is found to overcome a disadvantage recently discovered in catalytic hydrodewaxing.
Examination of the properties of fractions of lubricating stocks from catalytic hydrodewaxing has shown that the lower boiling portions of the stock have low viscosity index.
This contrasts with solvent dewaxing which preserves the VI values throughout the boiling range of the dewaxed oil.
This effect of catalytic hydrodewaxing is overcome by operating in the manner of this invention whereby the lighter portions of the charge are subjected to milder conversion conditions conducive to retention of high VI across the full boiling range.
As will be recognized, catalytic dewaxing of fuel fractions can also be practiced in the same manner.
In that case the process can include hydrotreating for removal of sulfur, nitrogen, metals and the like through packing in part of the column with a suitable hydrotreating catalyst.
The charge to the process is introduced to an intermediate point in the packed column, such that a substantial portion of catalyst constitutes packing both above and below the feed point.
The distillation column need not be packed only with catalysts.
Catalysts may be deposited as a coating on conventional packing materials such as Raschig rings, etc.
The packing may be interspaced with bubblecap plates or perforated plates.
See FIG.
1.
Temperature control along the length of the column is maintained at the desired gradient values by cooled reflux to the top of the column and circulation of liquid from the bottom through a heat exchanger